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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of stepped-well and square-well multiple-quantum-well optical modulators (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1411-1414 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The responsivity and transmission performance of 60-period p-i-n multiple-quantum-well (MQW) optical modulators having single or double steps in the quantum well (QW) has been experimentally compared to a square-QW control sample. It has been confirmed that significantly increased shift of the exciton with applied electric field [the quantum confined Stark effect (QCSE)] is obtained in the stepped QWs as compared to a conventional square QW. However, no meaningful increase in optical modulation performance is found, due to broadening of the exciton transition in the stepped QWs. All MQWs contained nominal 45 A(ring) Al0.3Ga0.7As barriers. Single-step QWs consisted of a 15 A(ring) GaAs region with an 85 A(ring) Al0.1Ga0.9As step. Double-step QWs consisted of a central Al0.15Ga0.85As plateau, with 20 A(ring) GaAs regions on either side. The square QW consisted of 90 A(ring) of GaAs. Excellent agreement between measured QCSE and tunneling resonance calculations was found. Our results indicate that stepped MQW devices are intrinsically more susceptible to growth induced degradation than square MQW modulators. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360297
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  • 2
    Electronic Resource
    Electronic Resource
    GaAs-AlAs low-voltage refractive modulator operating at 1.06 μm (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 744-746 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have produced a nonabsorbing surface-normal optical modulator operating at 1.06 μm (e.g., for a high-power Nd-YAG pump laser) which has a relative transmission change of 16% for −1 to 1 voltage swing. The structure is a GaAs-AlAs dielectric mirror with alternating n- and p-type δ doping at each interface. Doping selective contacts are made to the sample so that an applied voltage appears equally across each period of the device, yielding a strong field which changes the index of the GaAs and hence shifts the mirror.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103432
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  • 3
    Electronic Resource
    Electronic Resource
    Fast escape of photocreated carriers out of shallow quantum wells (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 66-68 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report that at room temperature the field-induced escape of photogenerated carriers out of shallow GaAs/AlxGa1−xAs multiple quantum wells is as fast as for pure GaAs of the same thickness, if the value of x does not exceed 0.04. Our experimental findings can be explained by assuming that carriers are efficiently scattered into the unconfined barrier states by absorption of a LO phonon, as long as the effective barrier height is less than the LO-phonon energy. The application of shallow quantum wells with x≤0.04 in self-electro-optic effect devices, providing not only strong excitonic electroabsorption but also fast sweep-out times at small biases, should lead to shorter switching times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105524
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  • 4
    Electronic Resource
    Electronic Resource
    Excitonic electroabsorption in extremely shallow quantum wells (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2582-2584 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the remarkable observation of strong room-temperature excitonic features in the absorption spectra of GaAs-AlxGa1−xAs quantum wells (QWs) for values of x as low as 0.02. This has important implications for high-power modulators, since saturation intensities have been shown to be higher in QW modulators with low barriers. In addition, very shallow QWs have enhanced electroabsorption at small biases because of ease of ionization. In our p-i(multi-QW)-n device with x=0.02, we obtain a transmission change from 29% to 47% for a voltage change from +1 to −3 V.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103822
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  • 5
    Electronic Resource
    Electronic Resource
    Does luminescence show semiconductor interfaces to be atomically smooth? (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2666-2668 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Luminescence spectra from quantum wells are routinely interpreted in terms of atomically smooth and atomically abrupt interfaces. Here we show that this interpretation is inconsistent with photoluminescence, photoluminescence excitation, and quantitative microscopic (chemical lattice imaging) results. We argue that the discussion of interfacial roughness in terms of "an island size'' is too naive. A full characterization of an interface requires the description of a "roughness spectrum,'' specifying the amplitude of the interfacial corrugation versus corrugation wavelength over the relevant length scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102825
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  • 6
    Electronic Resource
    Electronic Resource
    Exciton saturation in electrically biased quantum wells (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2315-2317 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the heavy hole excitation saturation intensity in GaAs/AlGaAs quantum wells as a function of applied electric field and AlGaAs barrier design. We find that the saturation intensity increased with increasing applied field, and decreasing barrier thickness or height, because of increased carrier sweep-out rates. Time-resolved sweep-out time and temperature-dependent saturation intensity measurement point out the roles of both thermionic emission and tunneling in the field and barrier-dependent carrier escape time. By reducing the barrier Al composition from 30 to 20%, we achieved an increase in the saturation intensity by a factor of ∼6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104113
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  • 7
    Electronic Resource
    Electronic Resource
    Enhanced diffusion of Si due to He ion implantation in Si-delta doped GaAs layers (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2657-2659 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Enhanced diffusion of Si due to He ion implantation in Si-delta doped GaAs layers has been observed by the capacitance-voltage technique. After an 800 °C anneal, an increase as large as an order of magnitude in the diffusion coefficient compared to thermal diffusion was observed. We also observe a decrease in the integrated sheet carrier concentration as a result of the He implants, and the decrease appears independent of annealing time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102844
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  • 8
    Electronic Resource
    Electronic Resource
    Bias-controlled intersubband wavelength switching in a GaAs/AlGaAs quantum well laser (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1382-1384 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The light emission characteristic of a GaAs/AlGaAs single quantum well laser with an intracavity monolithic loss modulator has been investigated. Discrete, widely separated, wavelength switching from the first (875 nm) to the second (842 nm) subband is achieved by changing the applied modulator bias. In addition, we show that 2 mW of lasing light power may be modulated with a change in current of 250 μA and a voltage change of 1 V.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101601
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  • 9
    Electronic Resource
    Electronic Resource
    Hydrogenation of multiple-quantum-well optical-modulator structures (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2174-2176 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report studies of hydrogenated multiple-quantum-well (MQW) optical-modulator structures via electron-cyclotron-resonance-derived plasmas. Responsivity, optical transmission, current-voltage, and capacitance-voltage characterizations of Schottky- as well as pin-diode modulator structures were performed. We find photocurrent-collection efficiency and photoluminescence intensity to be enhanced by hydrogenation, with measurable improvement in electrically biased exciton-absorption linewidth also seen. We interpret our results as arising from increased carrier lifetime in the MQW region, because of passivation of deep levels/defects. The improvements were stable after 550 °C heat treatment. These effects may be useful for improving the yield of usable MQW devices grown in a given system. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112752
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  • 10
    Electronic Resource
    Electronic Resource
    Wavelength-selective detector based on a quantum well in a standing wave (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 134-136 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present an example of a new class of optoelectronic devices realized by placing thin absorbers in a standing wave. Using quantum wells as absorbers and measuring the photocurrent from each of them separately it is possible to realize devices which accomplish complex tasks like separately detecting more than one wavelength at the same time or measuring the wavelength of a quasimonochromatic beam. In this letter we demonstrate a wavelength-selective detector based on a single quantum well. It detects at 850 nm with a bandwidth 〈10 nm, while rejecting at the shorter wavelength of 835 nm by a factor of 120.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111542
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